Havoc Startup Minimizer Released

November 16, 2025

I've been a long-time Mozilla Thunderbird user and really like the email client - enough that I even donate to the project. Thunderbird includes a handy option that allows you to minimize the app to the system tray, which is great if you want it to keep running in the background.

However, there's still one missing piece: even if you enable that option and add Thunderbird to your Windows startup apps, so it launches automatically when you log in, it still can't start minimized.

I started wondering today whether an extension could handle this. I'm sure there are already extensions that can do that, but it seemed like a good opportunity to learn how difficult it is to build an extension myself. The result is Havoc Startup Minimizer - a lightweight, efficient, and permission-free extension for Mozilla Thunderbird that minimizes the main Thunderbird window immediately after startup.

You can find it on the official Thunderbird Add-ons site: https://addons.thunderbird.net/en-US/thunderbird/addon/havoc-startup-minimizer

And the source code is available on GitHub: https://github.com/Havoc7891/havoc-startup-minimizer